Conventional cellular radio systems which are currently in widespread use throughout the world providing telecommunications to mobile users are designed around a plurality of geographical cell areas, usually of nominally hexagonal shape, each cell being served by a base station with which a plurality of mobile stations within the cell communicate. By dividing a geographical area into the plurality of cell areas, carrier frequencies used to communicate between the base stations and mobile stations can be re-used from cell to cell. The number of mobile stations which can be supported within the geographical area is limited by the available number of carrier frequencies. Base stations are expensive, and require extensive effort in obtaining planning permission for their erection. In some areas, suitable base station sites may not be available. In general, an object of cellular radio communication system design is to have as few base stations as possible, whilst supporting as many mobile stations as possible. Consequently, it is an on-going objective of cellular radio communication system design to increase the traffic carrying capacity of base stations.
Where base stations are permitted, reasons of planning restrictions and cost may limit the size of masts and towers used to support antenna arrangements. Available space for antennas at the tops of towers is limited. It is another ongoing objective of cellular radio system design to provide coverage for a cellular area, using antennas having a minimum size and weight. Reduction in size and weight allows reduced size of mast or tower structures, and may make a difference between being able to deploy a base station or not. Additionally, having smaller antennas has manufacturing and transportation advantages relating to the antennas themselves.
A further problem encountered in cellular radio communication systems is that of signal fading. Signal fading may occur on an up-link communication between a mobile station and a base station due to multi-path reflections of a transmitted signal causing partial cancellation of each other at the base station.